CVE-2021-47343

In the Linux kernel, the following vulnerability has been resolved: dm
btree remove: assign new_root only when removal succeeds remove_raw() in
dm_btree_remove() may fail due to IO read error (e.g. read the content of
origin block fails during shadowing), and the value of shadow_spine::root
is uninitialized, but the uninitialized value is still assign to new_root
in the end of dm_btree_remove(). For dm-thin, the value of
pmd->details_root or pmd->root will become an uninitialized value, so if
trying to read details_info tree again out-of-bound memory may occur as
showed below: general protection fault, probably for non-canonical address
0x3fdcb14c8d7520 CPU: 4 PID: 515 Comm: dmsetup Not tainted 5.13.0-rc6
Hardware name: QEMU Standard PC RIP: 0010:metadata_ll_load_ie+0x14/0x30
Call Trace: sm_metadata_count_is_more_than_one+0xb9/0xe0
dm_tm_shadow_block+0x52/0x1c0 shadow_step+0x59/0xf0 remove_raw+0xb2/0x170
dm_btree_remove+0xf4/0x1c0 dm_pool_delete_thin_device+0xc3/0x140
pool_message+0x218/0x2b0 target_message+0x251/0x290 ctl_ioctl+0x1c4/0x4d0
dm_ctl_ioctl+0xe/0x20 __x64_sys_ioctl+0x7b/0xb0 do_syscall_64+0x40/0xb0
entry_SYSCALL_64_after_hwframe+0x44/0xae Fixing it by only assign new_root
when removal succeeds